Following up on the kernel summit tech topic presentation of ZONE_DEVICE, here is a re-post of dax-gup support patches. Originally posted back in September [1], this reduced set represents the core of the implementation and the changes most in need of review from -mm developers. [1]: https://lists.01.org/pipermail/linux-nvdimm/2015-September/002199.html --- To date, we have implemented two I/O usage models for persistent memory, PMEM (a persistent "ram disk") and DAX (mmap persistent memory into userspace). This series adds a third, DAX-GUP, that allows DAX mappings to be the target of direct-i/o. It allows userspace to coordinate DMA/RDMA from/to persitent memory. The implementation leverages the ZONE_DEVICE mm-zone that went into 4.3-rc1 (also discussed at kernel summit) to flag pages that are owned and dynamically mapped by a device driver. The pmem driver, after mapping a persistent memory range into the system memmap via devm_memremap_pages(), arranges for DAX to distinguish pfn-only versus page-backed pmem-pfns via flags in the new pfn_t type. The DAX code, upon seeing a PFN_DEV+PFN_MAP flagged pfn, flags the resulting pte(s) inserted into the process page tables with a new _PAGE_DEVMAP flag. Later, when get_user_pages() is walking ptes it keys off _PAGE_DEVMAP to pin the device hosting the page range active. Finally, get_page() and put_page() are modified to take references against the device driver established page mapping. The full set in context with other changes is available here: git://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm libnvdimm-pending A test to prove out the pmd path is here: https://github.com/pmem/ndctl/blob/master/lib/test-dax-pmd.c --- Dan Williams (5): mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd mm, x86: get_user_pages() for dax mappings dax: provide diagnostics for pmd mapping failures dax: re-enable dax pmd mappings arch/ia64/include/asm/pgtable.h | 1 arch/sh/include/asm/pgtable-3level.h | 1 arch/x86/include/asm/pgtable.h | 2 - arch/x86/mm/gup.c | 56 +++++++++++++++++++- drivers/nvdimm/pmem.c | 6 +- fs/Kconfig | 3 + fs/dax.c | 55 ++++++++++++++----- include/linux/huge_mm.h | 13 ++++- include/linux/mm.h | 89 ++++++++++++++++++++++++++----- include/linux/mm_types.h | 5 ++ kernel/memremap.c | 53 +++++++++++++++++-- mm/gup.c | 17 ++++++ mm/huge_memory.c | 97 +++++++++++++++++++++++++--------- mm/memory.c | 8 +-- mm/swap.c | 15 +++++ 15 files changed, 348 insertions(+), 73 deletions(-) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>